International Edition

  • Understanding Microsoldering Applications

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    BY LUCA CONTE, WELLER SALES MANAGER SOUTHERN EUROPE

    Many believe that a large soldering application is more difficult than a small one. However, this is not true because, in electronics, size truly does not matter. The thermal load of an application has the most impact due to the electrical (and so thermal) connections, the number and thickness of layers of the PCB, grounding layers, and eventual dissipators or other “heat sucking” parts/components. Not only must the component be heated, but also the pad and substrate, making it difficult to judge an application solely by looking at it. Because of this, microsoldering applications offer limited contact surface. Also, commonly used tip dimensions are small and require a technology that delivers an accurate temperature to the end of the tip. Small pads and tips also need precise temperature control to not damage the component/pad or result in cool down due to the heat requirement. This is one of the most common reasons for PCB/component damage as well as the inability to rework/repair a PCB.

    Microsoldering is a big world and includes a wide range of sizes and appli-cations that can be found in practically any printed circuit board. For this article, components smaller than 2×1 mm are considered for microsoldering.

    Specify
    Weller offers numerous tools split into three heating technologies for professional and general applications:

    1. Silver Line: The WSP80 with Silver Line technology offers efficient, cost-effective tips that are external to the heating element and sensor. This is ideal for general applications that do not have too big or too small of components and not too high of a heat request.
    2. Power Response: also this technology uses tips that are cost-effective and external to the heater WXP90 and WP/WXP65, both using XNT tips, could be a perfect solution with an interesting performance/running costs ratio.
    3. Active Tip tool technology combines the heating element, sensor and tip in a single body to enhance performance. It also is available in a military standard version. Active Tip allows for quick toolless tip change and, more importantly, provides fast heat up, reaction and recovery times. Because Active Tips have a price range higher than a standard tip, this technology could be used only for difficult application, eventually using the second channel of the control unit or even replacing the tool depending on the application. This is possible using Weller’s control units (WT2M, WR3M and all WX family). Other manufacturers only have one technology and each unit only controls one type of tool. Active tip technology is the ideal answer to high heating demand applications, especially on small components: with the MICRO tool, users easily tackle small and medium components, but for the smallest ones – or when heat demand is higher – PICO makes the difference. If the application’s heat requirement is not too heavy, WTP/

    Apply
    If a circuit’s thermal load is not relevant, WSP/WP/WXP80 and WP/WXP65 are precise and powerful enough to tackle the application. By increasing the thermal load (more grounding layers, dissipators/heat shrinks, etc.) the “technology” of the chosen tool also must be increased. In this case, WTP/WXP90 eventually could increase performance; however, the best solution is active tip technology, choos-ing between WMRP/WXMP or WXPP for the smallest applications. Tips and tools from both are available in military standard versions.

    Preheating is not a crime. It is useful and sometimes even essential. In Weller’s product range, there are several pre-heating plates with different dimensions and technologies, both standalone and those connected to a soldering control unit. Preheating plates are helpful while soldering but also for desoldering, for example with hot air: small components need the precision, focus and delicate air blow that tools like HAP100, HAP200 and WXHAP200 deliver. These tools are compatible with pneumatic control units (WR2, WR3M, WXR3) as well as those that must be connected to compressed air (WAD101, WXA2). For simple chips a valid alternative to hot air are thermal tweezers like WMRT and WXMT, that, by heating simultaneously both sides, heat both component side at the same time and allow to easily desolder and pick up the component.

    Additionally, using quality solder alloys can make a difference. Weller offers many options with M1 or L0 no-clean flux, in SAC, SC, SCN versions, different reels size and starting from 0.2 mm. Weller WSW soldering alloys provide 100 per-cent continuous single flux core, meaning that there is flux in every single section of the solder wire, increasing wettability, repeatability and productivity. Micro alloys reduce tip consumption and with WSW alloys, there are reduced splashes, increasing operator safety and workspace cleanliness (around both worked parts and the bench).

    For more information about Weller’s heating technologies as well as other advanced technology products, e-mail [email protected] or visit www. weller-tools.com.


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